Fig. 3. HPLC separation of major molecular species of (A) glycerophosphoethanolamines (GPEtns) and (B) glycerophosphocholines (GPChols) of P. apeterus thoracic muscle tissue. The upper most trace (in A and B) shows total GPEtn and GPChol fractions and the lower traces show individual ion masses (molecules), as they were extracted using the MS ion trap. Note that a relative y axis are used in all chromatograms, where the highest peak is taken as 100% response. That is why the signal/noise is relatively low in the rare species, e.g. 16:0/18:1-GPChol. For quantification purposes, the areas under chromatographic peaks of individual molecular species derived from a total chromatogram (upper traces) were compared.